Wait until the leaves start dropping (usually October) then take cuttings about 8-10 inches long of brown (not green) wood. Cut just below a bud at the bottom and just above a bud at the top. Remove any remaining leaves and then plant in ordinary soil or multi-purpose compost so that at least 4 buds are below the surface, with 2 or 3 above. Don't disturb until the same time next year when they can be transplanted into their final position or into a large pot. Blackcurrants are easy to propagate this way, so most cuttings should take providing you don't let them dry out at any stage.